Gallagher was scheduled to perform from 4:30-5:30 P.M. Central Time at this year’s Lollapalooza music festival in Chicago, but called it quits after only 20 minutes, citing vocal issues, says Billboard.

The singer even issued a quick apology via Twitter, writing, “Sorry to the people who turned up for the gig in Chicago lollapalooza had a difficult gig last night which [f–ed] my voice. I’m gutted LG x”

Despite the apology, fans aren’t having it. “Disappointed man. you could’ve at least told people on stage rather than just walking off,” replied one disgruntled Twitter user. “I waited 3 hours to be front row for you. My heart is broken,” wrote another.

Though Gallagher blamed shot vocal cords for his early exit, some people suspect other reasons. For example, one fan blames a sign that her friend held up at the show that read, “I <3 YOU NOEL.” Noel is Liam Gallagher’s brother and former Oasis bandmate, and according to Billboard, the two don’t exactly share a brotherly bond. Liam once reportedly referred to Noel as “a crazy celebrity stalker.”

Some are theorizing that the sign may have set him off. Or it could have been a case of “Liam being Liam” — as the rocker has a history of trouble making and moodiness. Or maybe it actually was his voice.

Other than Gallagher’s early departure, Billboard reports that the festival is going smoothly in its first day.